The present invention relates to a grained injection molded product, a method and a device for producing a grained injection molded product.
A method for the preparation of a grained injection molded product, i.e., an injection molded product with a grain-like pattern on the surface of the product from a synthetic resin is disclosed, for example, in Japanese Patent Application Laid-Open No. 8-276,464. This disclosed method is adaptable to the large-scale preparation of injection molded products from synthetic resin, which are provided with a grain-like pattern resembling a grain of a natural wood product.
This disclosed method can provide an injection molded product with a grain-like pattern on its surface; however, it cannot form a pattern of high quality such as a fine grain-like pattern.
Therefore, the present invention has the primary object to provide a grained injection molded product with a fine grain-like pattern remarkably resembling a wooden product with a natural grain pattern.
The present invention has another object to provide a method for the preparation of an injection molded product with such a grain-like pattern resembling a grain of a natural wooden product.
The present invention has a further object to provide a device for use in the preparation of an injection molded product with a grain-like pattern resembling a grain of a natural wooden product.
In order to achieve the first object as described above, the present invention provides a grained injection molded product on at least a surface of the injection molded product from a molten resin being composed of a first material and a second material having a color different from the color of the first material and combined in an incompletely mixed state, that is, in a substantially separately mixed state such that the first material and the second material are not completely mixed and separately combined so as to visibly distinguish the colors of the two materials from each other, the injection-molded product prepared by feeding the molten resin as in the form of divided streams into a cavity, elongating the divided streams into a desired shape of a product, and allowing the divided streams to solidify with traces of the divided streams in the form of a grain-like pattern retained on the surface of the product; wherein each of the divided streams is allowed to solidify into a solidification layer comprising a first solidification layer section and a second solidification layer section, the first solidification layer section being composed substantially of the first material and extending in a direction of elongation of the divided stream on the inside thereof and the second solidification layer section being composed substantially of the second material and extending in a direction of elongation of the divided stream on both sides thereof.
In order to further achieve the primary object, the present invention provides an injection molded product with a grain-like pattern on at least a surface of the injection molded product, prepared by feeding a molten resin composed of a mixture of a first material and a second material having a color different from that of the first material, combined in a substantially separately mixed manner, in the form of plural divided streams to a cavity, elongating the plural divided streams into the product, and allowing the plural divided streams to solidify with traces of the divided streams in the form of a grain-like pattern retained on at least the surface of the product; wherein the molten resin is allowed to solidify into a solidification layer with the trace of the divided stream retained thereon and a reinforcement member is disposed inside the solidification layer for supporting for the solidification layer; and wherein the solidification layer of each divided stream comprises a first solidification layer section and a second solidification layer section, the first solidification layer section being composed substantially of the first material and extending in a direction of elongation of the divided stream on the inside thereof and the second solidification layer section being composed substantially of the second material and extending in a direction of elongation of the divided stream on both sides thereof.
In order to achieve the second object, the present invention provides a method for the preparation of an injection molded product with a grain-like pattern, which comprises feeding a molten resin composed of a first material and a second material having a color different from that of the first material to a cavity resin feed end of a cavity, the molten resin being a mixture of the first and second materials in a substantially separately mixed manner; and feeding the molten resin into the cavity from the cavity resin feed end thereof as in the form of a plurality of divided streams.
In order to further achieve the second object, the present invention provides a method for the preparation of an injection molded product with a grain-like pattern, which comprises feeding a molten resin to a cavity resin feed end of a cavity with a reinforcement member set at a site corresponding to the inside of the injection molded product, the molten resin being composed of a first material and a second material having a color different from that of the second material and combined in a substantially separate manner; and feeding the molten resin from the cavity resin feed end thereof into a space of the cavity between the reinforcement member and a wall surface of the cavity in the form of a plurality of divided streams.
In order to achieve the third object, the present invention provides a device for use in the preparation of an injection molded product with a grain-like pattern, wherein a gate is disposed at the cavity resin feed end of the cavity; and the gate is arranged so as to flow the molten resin into the cavity in the form of plural divided streams in a parallel arrangement.
In order to further achieve the third object, the present invention provides a device for use in the preparation of an injection molded product with a grain-like pattern, wherein the reinforcement member is set at a site of the cavity corresponding to the inside of the injection molded product; and a plurality of gates are arranged sideways in a space between the reinforcement member and a wall surface of the cavity so as to flow the molten resin in the form of a plurality of divided streams into the cavity resin feed end of the cavity.
For the invention in the aspect, the molten resin composed of the first material and the second material having a color different from that of the first material and combined in a substantially separate manner is fed to the cavity in the form of a plurality of divided streams, and each of the divided streams composed of the second material enters into the cavity in a parabolic form by taking advantage of the flow characteristics of the plural divided stream and then disperses in a widthwise or transverse direction, i.e., toward the inside of the divided stream, while flowing toward the cavity resin reach end of the cavity. The widthwise extension of the end portion of the divided stream is restricted by the function that each of the adjacent divided streams acts as a sort of a wall of the divided stream, in association with the action that the end portion of the divided stream flows toward the cavity resin feed end thereof. However, while the widthwise extension of the divided stream of the first material is being restricted, the divided stream composed of the first and second materials is extended in a direction of elongation thereof and allowed to solidify with the trace of the divided stream retained thereon into a solidification layer, when solidified, that comprises a first solidification layer section and a second solidification layer section, the first solidification layer section being composed substantially of the first material and extending in a direction of elongation of the divided stream thereof on the inside thereof and the second solidification layer section being composed substantially of the second material and extending in a direction of elongation of the divided stream on both sides thereof. As the plural divided streams are solidified, the traces of the divided streams are left retaining a grain-like pattern having a generally constant width between all the adjacent lines on the surface. The injection molded product of the invention can form a fine grain-like pattern resembling a grain on a natural wooden material.
On the other hand, the second material of each divided stream has a transverse extension of the width thereof regulated from extending transversely, that is, on the inside of the divided stream, by the adjacent divided streams immediately after entry into the cavity, forming a linear pattern having a generally constant width, thereby forming a fine grain-like pattern resembling a grain of a naturally wooden material, whether the full length of the divided stream is longer or shorter.
Further, for the injection molded product with a grain-like pattern according to the present invention, a linear pattern can be formed depending upon a number of divided streams because a pattern with two lines is formed for every one divided stream. Therefore, the number of the lines of the linear pattern can be increased or decreased by adjustment of the number of the divided streams, so that a variety of fine grain-like patterns can be created in an optional manner.
Moreover, as a fine grain-like pattern can be formed following traces of the corresponding divided streams, such a fine grain-like pattern can be created on an injection molded product of a variety of shapes, such as an elbow-like shape or a cap-like shape, simply by setting the number of the divided streams upon molding. Therefore, the injection molded products can be manufactured at cheap costs, which are equal in quality to natural wooden products.
In addition, as the fine grain-like pattern is formed on the basis of the traces of the divided streams, the divided stream of the second material can create a linear pattern having a generally constant width within the inside as well as on the surface of the molded product on the basis of the action of the divided streams upon molding, so that the grain-like pattern of the injection molded product fails to disappear even if the injection molded product would wear off. Therefore, the injection molded product with the fine grain-like pattern increases reliability for a fine grain-like pattern as well as provides a fine grain-like pattern resembling a grain of a naturally wooden material. Moreover, the injection molded product can well compete with wearing off and abrasion.
A preferred aspect of the present invention can set to render thickness of the divided stream thicker at a site where the flow distance of each trace of the divided stream becomes longer in the direction of elongation of the trace thereof than the rest, so that a resistance to flow of the divided streams can be rendered smaller at the portion where the thickness is thicker at the stage of manufacturing the injection molded products with a fine grain-like pattern. Therefore, each divided stream can reach the cavity resin feed end of the cavity at a substantially equal timing, while suppressing the confusion of the divided stream section of the first material with the divided stream section of the second material, that is, while enhancing the directional properties of the divided streams and suppressing turbulence of the directional properties of the divided stream in resistance to the force on the basis of the other divided streams. This function can control the turbulence of an ordered arrangement of the divided streams, upon manufacturing, even in the case where the injection molded product is provided with a curved portion (that is, where the flow distances of the divided streams differ from one another at different portions), such a turbulence being caused by flowing the divided stream that has reached the cavity resin reach end of the cavity at a faster timing into a flowing region of the divided stream that yet reaches the cavity resin reach end thereof, on the basis of the great difference in the reaching timing. After the divided streams are allowed to solidify, a linear pattern (a fine grain-like pattern resembling a grain on a natural wooden material) having a generally constant width can be formed over the entire length of the injection molded product.
In accordance with the present invention, a depressed portion or a raised portion is provided on the inside surface of the cavity along the trace of the divided stream, and the depressed portion or the raised portion can function as a guide means that may vary a space for the thickness of the cavity at the stage of manufacturing the injection molded product with a fine grain-like pattern. This guide function can sustain a flow of the divided streams with appropriate directional properties and suppress the turbulence of an ordered arrangement of the divided streams, even if the cavity is provided with a curved portion and the flow distance of the divided streams is different from the rest. Moreover, the enhanced directional properties can assist in sustaining an ordered arrangement among the divided streams because each divided stream can resist the force that may cause disturbing the directional properties of the divided streams, even if such force would act thereon. Therefore, the characteristics of each divided stream can be utilized for sure, so that a linear pattern with a generally constant width can be created for each divided stream, even in the case where the injection molded product would have a curved portion (where the flow distance of the divided streams is different), and the formation of a fine grain-like pattern resembling a grain of a natural wooden material can be ensured.
In a preferred aspect of the present invention, the first material or the second material contains wooden powder, so that the injection molded product can provide a wood-like touch or feel like a natural wood material, as well as a natural wood-like appearance on the surface thereof. Furthermore, the injection molded product can have a specific heat as a wooden material has. These properties can further provide an improved natural wood-like quality for the injection molded product of this invention.
A preferred aspect of the present invention can provide the injection molded product in the form of a flat plate with a plurality of traces of the plural divided streams formed inside it as well as on its surface as in the form of a grain-like pattern in the direction of elongation of the divide streams. Therefore, the injection molded product has a fine grain-like pattern on the surface and inside thereof, which follows the traces of the divided streams, so that the cut surface of the molded product also has a fine grain-like pattern.
The present invention in a preferred aspect provides a cylindrical body with bottom having a ceiling part and a peripheral side wall part extending at a right angle from the peripheral edge section of the ceiling part, which is formed with traces of plural divided streams extending longitudinally from a portion of the peripheral side wall part on a one side of the cylindrical body to the other portion of the peripheral side wall part on the opposite side thereof. Therefore, even if the injection molded product would be such a cylindrical body with bottom, a fine grain-like pattern can be formed on the surface of the peripheral side wall thereof on the basis of the traces of the plural divided streams which extend longitudinally from a portion of the peripheral side wall part on a one side thereof via the ceiling part to the other portion of the peripheral side wall part on the opposite side thereof. This provides the surface of the ceiling part with a favored outlook as shown on a surface of a cut section of a natural wood with a fine grain.
Further, a preferred aspect of the present invention also provides a cylindrical member having an L-shaped curved portion, which is formed with traces of plural divided streams on the peripheral surface thereof extending along and parallel to the axis of the cylindrical body. Even if the injection molded product would be a product with a curved section such as an L-shaped section as in this aspect, the L-shaped molded product is provided on its entire surface area with a fine grain-like pattern that follows the traces of the plural divided streams extending along and parallel to the axis thereof, as if it would be formed by bending a natural wood material by laborious processing means.
In another aspect of the present invention, there is used a molten resin which is composed of the first material and the second material having a color different from that of the second material and which has the first material and the second material combined in a substantially separate state, and the molten resin is fed into the cavity as plural divided streams and allowed to solidify on a reinforcement member. In this aspect, the divided stream section composed mainly of the second material enters into the cavity in a parabolic form, together with the divided stream section of the first material, and then disperses in the widthwise direction of the partial section, while the top of each divided stream is elongating toward the cavity resin reach end of the cavity, on the basis of the flow characteristics of the divided stream. As the divided stream of the second material is flowing in the widthwise direction, the movement of the divided stream of the second material is regulated by a widthwise and forward movement of the divided stream of the first material that is flowing adjacent the divided stream of the second material. The divided stream is then allowed to solidify into a solidification layer leaving traces of the divided streams thereon, which comprises a first solidification layer section and a second solidification layer section, the first solidification layer section leaving the trace of the divided stream of the first material and extending along and in the direction of elongation of each divided stream on the inside thereof and the second solidification layer section leaving the traces of the divided streams of the second material and extending in the direction of elongation of the divided stream on the both sides thereof. A combination of the traces of the plural divided streams provides a linear pattern having a generally constant width, and the injection molded product is formed with a fine grain-like pattern on the surface thereof, which resembles a grain on a natural wooden material.
In this aspect of the invention, each divided stream of the second material is regulated so as to fail to disperse in the widthwise or transverse direction thereof by the adjacent divided streams of the first material, as it enters the cavity. This permits the formation of a linear pattern having a generally constant width, so that a fine grain-like pattern such as a grain-like pattern remarkably resembling a fine grain of a natural wood material can be formed over the entire surface of the molded product, whether the full length of the divided stream is longer or shorter.
Moreover, a linear pattern for the injection molded product according to the present invention may be formed depending upon the number of the divided streams and a pattern composed of two lines is formed for each divided stream. Therefore, the number of lines for the linear pattern can be adjusted with high freedom to form a variety of fine grain-like patterns, simply by changing the number of the divided streams.
In addition, a fine grain-like pattern is formed mainly on the basis of the traces of the plural divided streams, so that a variety of grain-like patterns can be formed on various shapes of molded products, for example, an elbow-like shape or a cap shape, simply by setting the divided streams so as to comply with such requirements, upon molding. Therefore, the injection molded products with a fine grain-like pattern of quality as high as natural wooden products can be produced at cheaper costs.
Furthermore, this aspect of the present invention can form a fine grain-like pattern on the basis of the traces of the divided streams, so that a linear pattern with a generally constant width can be formed inside as well as on the surface the injection molded product by the action of the divided streams upon molding, which follows the traces of the divided streams composed mainly of the second material. Therefore, the injection molded product with such a grain-like pattern can sustain its pattern over the entire thickness thereof as well as on the surface thereof, even if it would be worn away, so that the injection molded product can provide improved reliability as the injection molded product with a fine grain-like pattern. At the same time, the injection molded product can provide a fine grain-like pattern that remarkably resembles a grain on a natural wooden material and also sustains resistance to wearing off or abrasion.
In this aspect of the present invention, too, the space of the cavity corresponding substantially to the thickness of the product can be readily rendered narrower by means of the reinforcement member in order to increase a speed of flowing the divided streams under conditions of a constant injection pressure at the stage of manufacturing processes, so that a more clearly fine grain-like pattern on the basis of the traces of the divided streams can be formed. On the other hand, the reinforcement member can supplement the narrowed portion of the solidification layer to ensure a sufficient level of physical strength.
Moreover, the molten resin consisting of the first material and the second material of different kinds are allowed to solidify in a substantially separately blended state, i.e., in a substantially state such that the two materials exist in a substantially separate state o as to visibly distinguish the two materials from each other. Therefore, the solidification layer might become lower in physical strength as compared with the mixture where the two materials are mixed together completely; however, in this case, the reinforcement member can supplement the decreased strength of the solidification layer, thereby ensuring a sufficient level of strength as an injection molded product.
In a preferred aspect of the present invention, the reinforcement member is disposed so as to laminate the solidification layer so as to cover the entire area of the inner side thereof, and the thickness of the solidification layer can be rendered thicker at a portion where the length of the trace of the divided stream becomes longer in the direction of elongation of the divided stream than at a portion where the length of the trace of the divided stream becomes shorter. Therefore, even if the molded product is provided with a curved section (that is, the flow distances of the divided streams are different for one another), the resistance to flow of the divided stream can be rendered lower at the thicker portion of the solidification layer by adjusting the thickness of the reinforcement member, at the stage of manufacturing the injection molded product with a grain-like pattern so as to allow all the divided streams to reach the cavity resin reach end of the cavity at a substantially equal timing. At the same time, the directional properties of the divided streams can be enhanced, and the disturbance of the directional properties thereof can be suppressed in resistance to the forces on the basis of the other divided streams, thereby sustaining an ordered arrangement of the divided streams. Therefore, even in the case where the injection molded product is provided with a curved section where the flow distances of the divided streams are different, the disturbance of an ordered arrangement of the divided streams can be suppressed, which may be caused by the entry of the divided streams reaching the cavity resin reach end of the cavity on the great difference in timing to reach the cavity resin reach end thereof into a flowing region of the divided streams that do not yet reach the cavity resin reach end thereof. Therefore, a linear pattern having a generally constant width, which remarkably resembles a fine grain pattern on a natural wooden material, can be formed on the solidification layer over the entire length of the traces of the divided streams.
On the other hand, in this aspect of the present invention, although the thickness of the solidification becomes irregular, the reinforcement member corrects the irregular thickness to a constant thickness or a designed thickness as required by the molded product.
A preferred aspect of the present invention is configured such that the reinforcement member is disposed so as to laminate so as to cover the substantially entire inner surface area of the solidification layer and it is provided with a guide groove along the traces of the divided streams opposite to the solidification layer in such a manner that the solidification layer extends into the guide groove. This configuration of the guide groove can provide the flow of each divided stream with appropriately enhanced directional properties on the basis of the guide function of the guide groove, while suppressing the directional properties of each divided stream at the stage of manufacturing the injection molded product, even if the cavity would be provided with a curved section and the flow distances of the divided streams would be different at different portions. Moreover, the enhanced directional properties of the divided streams can assist in sustaining an ordered arrangement of the divided streams and resist the force to disturb the directional properties of the divided streams would act on the divided streams, even if the force would act on the divided streams. Therefore, the action of each divided stream can be utilized in a definite way and, even in the case where the injection molded product is provided with a curved section, i.e., where the flow distances of the divided streams are different at different portions, a linear pattern with a generally constant width can be definitely formed for each divided stream, thereby providing a fine grain-like pattern resembling a natural grain pattern.
Further, the inner side surface of the solidification layer becomes raised or depressed by the provision of the guide grooves. The thickness at the raised and depressed surface of the solidification layer, however, can be rendered constant by the lamination of the reinforcement member by adjusting the thickness of the reinforcement member or the inner surface of the solidification layer by the solidification layer. The provision of the reinforcement member can render the inner surface of the injection molded product flat and the thickness of the injection molded product constant, thereby achieving improved maneuverability and favorable appearance.
In addition, the guide grooves can increase the area of attachment of the solidification layer to the reinforcement member, thereby assisting in enhancing the strength of attachment between the two elements.
In a preferred aspect of the present invention, a plurality of the guide grooves are disposed so as to agree with an arrangement of the traces of divided streams and the plural guide grooves are set to become deeper at a site where the distance of each divided stream trace becomes longer in the direction of elongation of the divided stream, thereby enabling the effects to be achieved.
A preferred aspect of the present invention uses the first material or the second material, which may contain wooden powder. This feature can provide a visible appearance for the injection molded product, which resembles a natural wooden material with a grain. Further, this can assist in ensuring a touch and specific heat for the injection molded product as if it is like a wooden material, so that a wood-like feeling of the injection molded product can be improved.
In this aspect, too, the reinforcement member can supplement and reinforce the strength of the solidification layer to a sufficient extent due to a possible decrease in the strength by the addition of wooden powder. Further, this feature allows an increase in a rate of the wooden powder, so that a wood-like quality of the injection molded product can be improved.
The present invention in a preferred aspect provides the injection molded product with a fine grain-like pattern, wherein the solidification layer is in the form of a flat plate and the divided stream traces are formed in the direction of elongation of the solidification layer. Therefore, the thickness of the injection molded product can be set to become as predetermined on the basis of the functions of the reinforcement member for reinforcement and adjustments of the thickness, and the inner surface of the solidification layer. This can also render the inner surface of the injection molded product flat, while ensuring the sufficient level of strength, favorable maneuverability and better appearance, and form a fine grain-like pattern on the surface of the injection molded product in the flat plate form and inside it (within the solidification layer), on the basis of the traces of the plural divided streams.
In a preferred aspect of the present invention, the injection molded product is in the form of a cylindrical body with bottom, wherein the solidification layer comprises a ceiling part and a peripheral side wall part extending at a right angle from the peripheral edge of the ceiling part and wherein the traces of the plural divided streams are created extending longitudinally from a portion of the peripheral side wall part on the one side of the cylindrical body to a portion of the peripheral side wall part on the other side thereof opposite to the one side thereof. The cylindrical body of this aspect of the invention can ensure a sufficient degree of strength, favorable maneuverability and better appearance by the provision of the reinforcement member. Furthermore, the injection molded product is provided with a fine grain-like pattern following the traces of the plural divided streams of the second material extending longitudinally from a portion of the peripheral side wall part on the one side of the cylindrical body via the ceiling part to a portion of the peripheral side wall part on the other side thereof opposite to the one side thereof. Moreover, the surface of the ceiling part can be shown to have a fine grain-like pattern formed on the basis of the plural divided stream traces, as if it is a cut section of a fine grain of a natural wooden material.
A preferred aspect of the present invention provides a cylindrical body with the solidification layer formed in a generally L-shaped form, wherein the traces of the plural divided streams are formed, extending along and parallel to the axis of the cylindrical body. Therefore, the injection molded product can be formed having a desired degree of strength and thickness on the basis of the functions of the reinforcement member for reinforcement, adjustment of thickness, and adjustment of the inner surface of the injection molded product. Moreover, this aspect of the present invention can render the inner surface (the inner peripheral face) of the injection molded product flat, while ensuring the desired level of strength, favorable maneuverability, and better appearance. In addition, in the case where the cylindrical body as the injection molded product is provided with a curved section such as a L-shaped curved section as in this embodiment, an ordered arrangement of a fine grain-like pattern can be formed on such a curved section as well as the peripheral surface along and parallel to the axis of the cylindrical body on the basis of the traces of the plural divided streams. Furthermore, the fine grain-like pattern of the injection molded product resembles a grain pattern on a natural wooden material prepared by laborious and complicated processing.
In a preferred aspect of the present invention, the reinforcement member is made of synthetic resin so that the reinforcement member can be better adapted to the solidification layer and it can be integrally joined together with the solidification layer. Further, if the color of the reinforcement member is the same as that of the solidification layer, they can be recognized as an integral thing.
Moreover, this aspect of the present invention can optionally form the injection molded product having an optional inside shape without disturbing the ordered formation of a grain-like pattern on the solidification layer, so that there can readily be produced projection elements or other parts for engagement or for use in accordance with partner elements for mounting or reinforcement ribs and so on for enhancement of strength.
A further aspect of the present invention provides a method for the preparation of the injection molded product with a grain-like pattern, wherein the molten resin composed of the first material and the second material having a color different from that of the first material and admixed in a substantially separate state is fed to the cavity resin feed end of the cavity. The second material is fed one after another as plural divided streams to the cavity resin feed end of the cavity, creating a shape of a flow extending along the cavity resin feed end thereof. Thereafter, the molten resin is fed from the cavity resin feed end into the cavity as a plurality of divided streams. In this instance, the second material of the molten resin undergoes the force (the injection pressure) of flowing in the direction crossing at a right angle to the cavity resin feed end thereof at the portion where each divided stream is created and each divided stream enters into the cavity in a parabolic form. Once each divided stream enters into the cavity, the top edge of each divided stream flows toward the cavity resin reach end of the cavity and begins spreading in the widthwise direction of each divided stream, while elongating along and parallel to the direction of elongation of the divided stream. The widthwise extension of the divided stream of the second material, however, is regulated by the action of the adjacent divided streams, and the divided stream of the second material is caused to elongate in the direction along and parallel to the direction of elongation of the divided stream while the divided stream of the second material is being suppressed from expanding in the widthwise or transverse direction of the divided stream. In particular, as each divided stream has a greater speed gradient on both sides than on the inside of the divided stream, the divided stream of the second material (forming a linear pattern) on the both sides of each divided stream of the first material is elongated to a divided stream having a narrower width by the shear force in the flow direction of the divided stream, and the linear pattern can be rendered gradually narrower as the divided stream is elongated longer. This can provide the injection molded product with a linear pattern having a generally constant width, which follows the divided stream traces, resembling a grain pattern on the surface of a natural wooden material.
Further, each divided stream of the second material is regulated immediately from the start of entry into the cavity resin feed end of the cavity by the adjacent divided streams of the first and second materials so as to fail to expand in a widthwise or transverse direction of each divided stream, so that a linear pattern with a generally constant width can be formed in the direction of elongation of each divided stream. This fine grain-like pattern resembling a grain on a natural wooden material can be formed on the surface of the injection molded product, whether it is longer or shorter.
Moreover, the pattern of the second material may depend mainly upon the number of divided streams because a pattern of two lines is formed for each divided stream, so that increasing or decreasing the number of divided streams can adjust the number of linear patterns. Therefore, a variety of fine grain-like patterns can optionally be formed on the surface of the injection molded product simply by adjusting the number of the divided streams.
Furthermore, the fine grain-like pattern is formed on the surface of the injection molded product on the basis of the divided streams, so that it can be formed over the entire surface area (the entire periphery) of the injection molded product simply by setting the divided streams for a moldable product of various shapes such as an elbow-like shape or a cap shape.
In addition, the fine grain-like pattern can be formed on the basis of the divided streams in a regular manner, so that the quality of the injection molded product (the state of the fine grain-like pattern formed) can be rendered uniform and raise a yield of the injection molded products.
This aspect of the present invention also provides the method for the preparation of the injection molded product with a grain-like pattern, which uses the molten resin comprising the first material and the second material having a different color in a substantially separately mixed state and feeds the molten resin to the cavity resin feed end of the cavity. This method in this aspect of the present invention utilizes the flow of the divided streams to create a flowing shape of the divided stream in front of the cavity resin feed end thereof, which then flows in the direction of elongation of the divided stream along the cavity resin feed end thereof by using any appropriate molding machine capable of feeding the molten resin into the cavity. Such a molding machine may include, for example, a screw-type injection molding machine, a plunger-type injection molding machine, a one-head injection molding machine or a multi-head injection molding machine. This method for the preparation of the injection molded product can reduce costs of plant and equipment because such a general-purpose molding machine can be used.
For the method in a preferred aspect of the present invention as described in claim 18, the divided streams can be fed into the cavity at substantially the same timing, so that the extension of each divided stream of the second material in the widthwise direction of the divided stream can be regulated immediately after the entry into the cavity to form a linear pattern having a generally constant width for each divided stream. The formation of the linear patterns by the divided streams of the second material utilizes the action of the adjacent divided streams of the first material, like a sort of the action functioning as a wall for regulating the flow of the divided stream of the second material immediately after the creation of the divided stream (immediately after the entry of the molten resin into the cavity). This can create a fine grain-like pattern resembling a grain on a natural wooden material, whether the size of the product is longer or shorter.
In a preferred aspect of the present invention, the plural divided streams are formed by the plural gates arranged sideways along the cavity resin feed end of the cavity, so that the plural divided streams can be created by the simplified process and device configurations with certainty and readiness.
Further, the method in a preferred aspect of the present invention can create a balanced mode of the flow of the divided streams over the entire range from the cavity resin feed end of the cavity to the cavity resin reach end thereof by regulating the movement of each of the divided streams having different magnitudes of the flow force injected from the plural gates (by means of a resistance to shear) by using a film gate communicating with each gate, which is disposed adjacent the gates, in association with the plural gates. Therefore, a linear pattern of each divided stream having a generally constant width can be sustained over the entire width, and the injection molded product with a grain-like pattern can be formed resembling a grain of a natural wooden material without causing any variation in the width of the linear pattern.
The method in a preferred aspect of the present invention can feed the divided streams into the cavity at substantially the same timing by adjusting the timing of feeding the divided streams on the basis of the resistance of the gates by rendering the gate size smaller for the gate that feeds the divided stream at a faster timing than the gate that feeds it at a slower timing. Therefore, a linear pattern with a generally constant width can be created surely for each divided stream, and the injection molded product with a fine grain-like pattern resembling a fine grain on a natural wooden material can be produced, whether it is longer or shorter.
In a preferred aspect of the present invention, an opening valve is disposed at the cavity resin feed end of the cavity, and the valve is opened as the portion in front of the cavity resin feed end thereof is filled with the molten resin. As the valve is opened, the molten resin is fed in the form of divided streams into the cavity at substantially the same timings. In this case, too, a linear pattern having a generally constant width can be certainly created for each divided stream, and utilizing the flow characteristics of each divided stream can produce the injection molded product with such a grain-like pattern resembling a fine grain on a naturally wooden material, whether it is longer or shorter.
The method in a preferred aspect of the present invention can sustain the flow of each divided stream with appropriate directional properties and suppress the disturbance of the directional properties of each divided stream by means of a guide means for guiding each divided stream, which may comprise a depressed section or a raised section and disposed at the portion of the cavity corresponding to the inside of the injection molded product. Therefore, the guide means can act efficiently on a curved section of the cavity (corresponding to the curved section of the injection molded product) where each divided stream has a different flow distance, and each divided stream can follow the guide means to form a grain pattern on the injection molded product. Moreover, the guide means can supplement the directional properties for each divided stream, so that the divided streams can sustain their ordered arrangement in resistance to the force of disturbing the directional properties, even if such force would act thereonto. This aspect of the present invention can certainly create a linear pattern with a generally constant width for each divided stream and produce the injection molded product with a fine grain-like pattern resembling a grain of a natural wood material on the basis of the action of each divided stream, even if the cavity is provided with a curved section corresponding to a curved part of the injection molded product, where the flow distance of the divided stream is different.
In a preferred aspect of the present invention, the resistance to the flow of each divided stream in the cavity can be rendered smaller at the site where the flow distance of the divided stream is longer relative to at the site where the flow distance of the divided stream is shorter. In this configuration, the divided stream becomes more likely to flow at the site of the cavity where the divided stream has a relatively longer flow distance than at the site where it has a relatively shorter flow distance, so that each divided stream can flow at nearly the same timing at every portion of the divided streams and reach the cavity resin reach end of the cavity at substantially the same time. Moreover, as the divided stream is arranged so as to become more likely to flow at the site where the divided stream having the relatively longer flow distance flows, the directional properties of the divided stream is supplemented and the disturbance of the directional properties of the divided stream can be suppressed in resistance to the force of the other divided streams, even if the force of disturbing the directional properties would act thereonto. Therefore, even in the case where the cavity is provided with a curved section corresponding to the curved section of the injection molded product, where the flow distance of the divided stream is different from one another, the disturbance of an ordered arrangement of the divided streams may be suppressed by the fact that the divided streams reaching the cavity resin reach end of the cavity at a faster timing enters into a flow region of the divided streams that do not yet reach the cavity resin reach end thereof on the basis of the big difference in the timing of reaching the cavity resin reach end of the cavity among the divided streams. This can ensure the sure formation of a linear pattern for each divided stream, which has a generally constant width among the divided streams and resembles a fine grain of a natural wooden material.
For the method in a preferred aspect of the present invention, the resistance to the flow of the divided streams can specifically be reduced because the means for reducing the resistance to the flow of the divided stream is designed so as to render the space corresponding to the thickness of the cavity relatively thicker in the flow region of the divided streams.
The method in a preferred aspect of the present invention can more efficiently exhibit the effects as achieved by the invention, even in the case where the cavity is provided with a curved section corresponding to a curved portion of the injection molded product wherein the flow distances of the divided streams are different from each other, because the guide means can elongate the divided streams longer at the site where the flow distance of the divided stream is longer than at the site where it is shorter.
In a preferred aspect of the present invention, the plural divided streams are created by using a plurality of gates disposed sideways along the cavity resin feed end of the cavity, together with the film gate disposed adjacent the gates and communicating with the gates. Further, the plural divided streams are guided by the guide means at the site of the cavity corresponding to the inside of the injection molded product, so that the effects as achieved by the invention can simultaneously be gained.
For the method in a preferred aspect of the present invention, the guide means is constituted by a plurality of guide grooves that can guide the divided streams at the site of the cavity corresponding to the inside of the injection molded product, and the guide grooves are disposed elongating longer at the site where the flow distance of the divided stream is longer than at the site where it is shorter. Therefore, the divided streams can be guided by the guide grooves so as to fail to disperse too widely in the widthwise direction of the divided stream. Moreover, the divided streams can be arranged so as to resist the force of disturbing or bending the flow direction of the divided streams. In addition, these functions can be exhibited effectively even in the case where the cavity is provided with a curved section corresponding to the curved portion of the injection molded product, that is, where the flow distance of each divided stream is different at different portions.
In a further aspect of the present invention, the cavity is disposed with the reinforcement member at the site corresponding to the inside of the injection molded product, and the molten resin composed of the first material and the second material having a color different from that of the first material and combined in a substantially separate state is fed to the cavity resin feed end of the cavity. Therefore, the divided stream of the second material of the molten resin is fed one after another on the basis of the feed flow of the molten resin, creating a flowing shape of the second material extending along the cavity resin feed end thereof. Thereafter, the molten resin is fed from the cavity resin feed end thereof in the form of plural divided streams into a clearance between the reinforcement member and the wall surface of the cavity. In this instance, the second material undergoes the force (the injection pressure) of flowing in the direction intersecting at a right angle to the cavity resin feed end of the cavity at the portion where each divided stream is created, then each divided stream flowing in a parabolic form into the clearance interposed between the reinforcement member and the wall surface of the cavity. After the divided streams have passed through the clearance of the cavity, then the top portion of each divided stream of the second material flows ahead on the reinforcement member toward the cavity resin reach end of the cavity while attempting to disperse in the widthwise direction of the divided stream. The widthwise extension of the divided stream of the second material, however, is then regulated by the adjacent divided streams, and each divided stream is elongated in the direction of the flow of the divided stream. In particular, for each divided stream, the speed gradient on both transverse sides in the widthwise direction of the divided stream is larger than the speed gradient on the inside in the widthwise direction thereof, so that the divided stream of the second material on the both transverse sides thereof (a linear pattern formed following the divided streams of the second material) is elongated by the shear force acting in the flow direction of each divided stream. The linear pattern is rendered narrower as the divided stream flows longer. The arrangement of the divided streams can create a grain-like pattern that has a generally constant width for each divided stream and extremely resembles a grain on a natural wood material, when the divided streams are allowed to solidify on the reinforcement member as a solidification layer. Therefore, this method can provide an injection molded product with a clear and fine grain-like pattern resembling a grain on a natural wood material.
Further, the second material of each divided stream can surely create a linear pattern having a generally constant width because the widthwise extension of the divided stream is regulated by the adjacent divided streams immediately after the entry of each divided stream into the cavity. Therefore, a fine grain-like pattern resembling a grain of a natural wooden material can be formed on the injection molded product whether it is longer or shorter.
Moreover, the linear pattern can be created in accordance with the number of the divided streams (two lines of a pattern being created for each divided stream), so that the number of the linear pattern can be increased or decreased optionally by adjusting the number of the divided streams, and a variety of fine grain-like patterns can optionally be formed on the surface of the injection molded product.
In addition, the method in this aspect of the present invention can form the fine grain-like patterns depending upon the divided streams for injection molded products in a variety of shapes such as an elbow-like shape or a cap shape, simply by setting the divided streams upon molding. This method can form the fine grain-like pattern on the entire periphery of the injection molded product.
Furthermore, this method can create the fine grain-like pattern on the basis of the divided streams in a regular manner, so that the quality of the molded product, that is, the state of the fine grain-like pattern formed, is rendered uniform and a yield of the injection molded products can be raised.
Furthermore, in the method in this aspect of the present invention, the molten resin is fed to the cavity resin feed end of the cavity in such a state in which the first material is blended with the second material in a substantially separate manner, and the divided stream of the second material can assume a flowing shape of the divided stream of the second material extending along the cavity resin feed end of the cavity in the position in front of the cavity resin feed end thereof. For this method, accordingly, any molding machine can be used as long as it has the function of feeding the molten resin to the cavity, and it may include, for example, a general purpose injection molding machine, such as a screw-type injection molding machine, a plunger-type injection molding machine, a one-head injection molding machine, or a multi-head injection molding machine. The use of such a general purpose injection molding machine can reduce costs of plant and equipment for manufacturing the injection molded products.
The method in this aspect of the present invention can also create the fine grain-like pattern on the basis of the divided streams clearly on the injection molded product by rendering the space of thickness of the cavity narrower by the disposition of the reinforcement member and as a consequence increasing the speed of the divided stream flowing under conditions of constant injection pressure at the stage of manufacturing the injection molded product. On the other hand, the reinforcement member can supplement the thinned portion of the solidification layer while ensuring a sufficient and desired amount of strength.
Furthermore, in the method in this aspect of the present invention, the molten resin is allowed to solidify in such a state that the first and second materials of different kinds are mixed in a substantially separate manner. Even if the strength of the solidification layer of the molten resin would be rendered lower as compared with the molten resin in which the first material and the second material are mixed completely, the reinforcement member can function as a supplement for the increased strength of the solidification layer, thereby ensuring the sufficient amount of strength as the injection molded product.
In the method according to a preferred aspect of the present invention, an interval between the reinforcement member and the wall surface of the cavity can be adjusted in accordance with the status of disposition of the reinforcement member so as to become relatively thicker at the site where the flow distance of each divided stream is longer in the direction of the flow of the divided stream. Therefore, the divided stream can be rendered more likely to flow simply by the adjustment of the reinforcement member at the site where the flow distance of each divided stream is relatively longer, so that each divided stream can be adjusted so as to reach the cavity resin reach end of the cavity at nearly the same timing. Moreover, the likelihood of the divided streams to flow at the identical timings can enhance the directional properties of the divided streams at the site where the flow distance of the divided stream is relatively longer, so that the disturbance of the directional properties of the divided stream can be suppressed in resistance to the force of disturbing the directional properties of the divided stream, even if the force would act upon the divided streams. This can also suppress the disturbance of an ordered arrangement of the divided streams, even if the cavity is provided with a curved section corresponding to the curved portion of the injection molded product and the flow distances of the divided streams are different from one another, the disturbance being otherwise caused by the fact that the divided streams reaching to the cavity resin reach end of the cavity reach faster enter into a flowing region of the divided streams that do not yet reach the cavity resin reach end thereof on the basis of the big difference in timing of the divided streams reaching the cavity resin reach end thereof. Therefore, a linear pattern with a generally constant width resembling a grain of a natural wood material can be formed on the entire length for each divided stream.
Further, in this aspect of the present invention, the thickness of the solidification layer becomes irregular, so that the reinforcement member to render the thickness of the injection molded product constant or thick as required by the design because the reinforcement member can correct the irregular thickness of the solidification layer.
Moreover, the substantial interval of the cavity for the thickness of the injection molded product can be adjusted by the reinforcement member, not by a mold, so that the adjustment can be effected readily as compared with the adjustment by means of the mold itself.
The method in a preferred aspect of the present invention can achieve the effects as achieved by the invention by specifically utilizing the adjustment of thickness by the reinforcement member as a flow resistance adjustment means for adjusting the flow resistance of each divided stream because the adjustment of an interval between the reinforcement member and the wall surface of the cavity is effected by the adjustment of thickness by the reinforcement member.
Furthermore, in the invention in a preferred aspect, guide grooves are disposed in a space between the reinforcement member and the wall surface of the cavity and each of the divided streams is guided by the guide groove. Therefore, even in the case where the cavity is provided with a curved section corresponding to the curved portion of the injection molded product, i.e., where the flow distances of the divided streams are different at different portions, each divided stream is allowed to flow with the directional properties in accordance with the guide grooves disposed on the reinforcement member, and the disturbance of the directional properties is suppressed by the disposition of the guide grooves. Moreover, this configuration allows an ordered arrangement of the divided streams on the basis of the supplement of the directional properties of each divided stream because each divided stream can resist the force of disturbing the directional properties of each divided stream even if the force would act upon it. Therefore, even if the cavity is provided with a curved section corresponding to the curved portion of the injection molded product and the flow distances of divided streams are different from one another, the reinforcement member ensures a sufficient amount of strength, and a linear pattern with a generally constant width can be created for each divided stream on the basis of the action of each divided stream. Therefore, a fine grain-like pattern resembling a natural grain of a wooden material can be formed on the injection molded product.
In this aspect of the method as described above, the solidification layer is provided with the depressed and raised portions on the inside thereof by means of the guide grooves, however, the irregular thickness of the solidification layer can be rendered constant by the provision of the reinforcement member (by the functions of the reinforcement member to adjust the thickness and the inner surface) which laminates the solidification layer. Therefore, the inside surface of the injection molded product can be rendered flat so that easy maneuverability and better appearance can be achieved.
Moreover, the guide grooves can increase the area of attachment of the reinforcement member to the solidification layer, so that the strength of attachment between the two elements can be enhanced.
In addition, the injection molded product can be produced more readily by forming the reinforcement member in the guide grooves, as compared with the formation in the mold.
In a further aspect of the present invention, the device for use in the preparation of the injection molded product with a grain-like pattern is provided with a gate at the cavity resin feed end of the cavity, which is disposed so as to flow the molten resin into the cavity in a side-by-side arrangement of plural divided streams. The device can produce the injection molded product with a grain-like pattern by utilizing the characteristics of the plural divided streams.
The device in a preferred aspect of the present invention contains a plurality of the gates arranged sideways. This mode of the device can form a plurality of the divided streams and eventually produce the injection molded product with a grain-like pattern.
The device in a preferred aspect of the present invention contains the plurality of the gates comprising overlap gates. For the device of this invention, the flow direction (a passage) of the molten resin entered into the overlap gates is changed inside the device, so that the best possible balanced flow of the divided streams can be created by each of the overlap gates on the basis of the change of the flow direction of the molten resin entered into the overlap gates. Therefore, a linear pattern can be sustained in a generally constant width over the entire length for each divided stream. Accordingly, this device can produce the injection molded product with a grain-like pattern resembling a natural grain on a wooden material having less variation in the width of the line of the linear pattern.
In a preferred aspect of the present invention, a film gate communicating with each of the plural divided streams is disposed adjacent the plural divided streams at the cavity resin feed end of the cavity. The device can act in the like manner as in the method, so that it can produce the injection molded product with a grain-like pattern resembling a fine grain pattern on a natural wooden material without less variation in the width of the linear pattern, whether the length of the pattern is longer or shorter.
For the device in a preferred aspect of the present invention, the gate is disposed so as to create a plurality of divided streams by locating a plurality of partitions for the fan gate. Therefore, the device can form the plurality of the divided streams and eventually produce the injection molded product with a grain-like pattern.
For the device in a preferred aspect of the present invention, the cavity resin feed end of the cavity is provided with the film gate disposed adjacent the plural gates and communicating with the inside of the gates. Therefore, this device can act in substantially the same manner as by the method and produce the injection molded product with a fine grain-like pattern resembling a grain on a natural wood material, without large variation in width of the pattern, whether the full length of the divided streams is longer or shorter.
In a preferred aspect of the invention, the device is provided with the passage of the cavity for the molten resin reaching the gates which has a curved passage section, so that the curved passage section of the device can suppress the disturbance of the flow of the molten resin and stabilize the injection pressure in front of the gates, so that each divided stream formed by the gates can be stabilized in the passage portion reaching the gates.
For the device in a preferred aspect of the present invention, the opening valve is provided at the cavity resin feed end of the cavity, and the opening valve is set so as for the plural divided streams to flow simultaneously into the cavity from the cavity resin feed end thereof at the time of opening the valve. Therefore, the device can act in substantially the same manner as by the method and produce the injection molded product with a grain-like pattern resembling a fine grain-like pattern of a natural wooden material without a great variation in the width of the linear pattern by equalizing the timing of feeding each divided stream, whether the full length of the divided stream is longer or shorter.
For the device in a preferred aspect of the present invention, the resistance to the flow in the gates are set to become relatively greater at the site of the cavity where the timing of feeding the divided streams into the cavity becomes faster. The device can adjust the timings of feeding the divided streams on the basis of the adjustment of the resistance to the flow of the divided streams so as to become equal to one another. Further, this device can produce the injection molded product with a grain-like pattern resembling a fine grain-like pattern of a natural wood material without a great variation in the width of the linear pattern, whether the full length of the divided stream is longer or shorter.
For the device in a preferred aspect of the present invention, the device is provided with a guide means for guiding each divided stream at the site of the cavity corresponding to the inside of the injection molded product with a grain-like pattern. The device in this aspect can act in the like manner as in the method and produce the injection molded product with a grain-like pattern resembling a grain on a natural wooden material without a big variation of the width of the linear pattern on the basis of the function of the guide means, whether the full length of the divided stream is longer or shorter.
The device in a preferred aspect has the thickness space in the cavity rendered thicker at the site of the cavity where the flow distance of the divided stream is relatively longer than at the site where the divided stream is shorter. This device can act in substantially the same manner as in the method and produce the injection molded product with a grain-like pattern resembling a grain on a natural wooden material without a big variation in the width of the linear pattern, whether the full length of the divided stream is longer or shorter.
For the device in a still further aspect of the present invention, the reinforcement member is disposed at the site of the cavity corresponding to the inside of the injection molded product, and a plurality of the gates are arranged sideways in a space interposed between the reinforcement member and the wall surface of the cavity, and the reinforcement member is set so as for the molten resin to flow sideways in the form of plural divided streams. Therefore, the device can produce the injection molded product with a grain-like pattern by utilizing the action of the plural divided streams on the reinforcement member.
For the device in a preferred aspect of the present invention, the interval interposed between the reinforcement member and the wall surface of the cavity is set to become relatively thicker by means of the reinforcement member at the site of the cavity where the flow distance of each divided stream becomes longer in the direction of the flow of each divided stream. Therefore, the device can act in substantially the same manner as in the method in the aspect of the present invention on the basis of the easy adjustment of the intervals by using the reinforcement member. Furthermore, this device can surely form a linear pattern resembling a grain on a natural wooden material having a generally constant width over the entire length of each divided stream even in the case where the cavity is provided with a curved section corresponding to the curved portion of the injection molded product and where the flow distances of the divided streams are different from one another.
The device in a preferred aspect of the present invention is provided with the reinforcement member having a plurality of guide grooves at a clearance between the reinforcement member and the wall surface of the cavity, and the guide grooves are disposed sideways extending toward the direction of the flow of each divided stream. This device can further form a linear pattern having a generally constant width for each divided stream on the basis of the action of each divided stream and produce a fine grain-like pattern resembling a grain on a natural wooden material, while the reinforcement member ensures a sufficient degree of strength for the injection molded product.
Moreover, the guide grooves are provided for the reinforcement member so that they can be formed more easily when it is formed directly on the mold.